Multichannel audio content corresponds to a speaker configuration having a certain number of channels. For example, multichannel audio content may correspond to a speaker configuration with five front channels, four surround channels, four ceiling channels, and a low frequency effect (LFE) channel. Such channel configuration may be referred to as a 5/4/4.1, 9.1+4, or 13.1 configuration. Sometimes it is desirable to play back the encoded multichannel audio content on a playback system having a speaker configuration with fewer channels, i.e. speakers, than the encoded multichannel audio content. In the following, such a playback system is referred to as a legacy playback system. For example, it may be desirable to play back encoded 13.1 audio content on a speaker configuration with three front channels, two surround channels, two ceiling channels, and an LFE channel. Such channel configuration is also referred to as a 3/2/2.1, 5.1+2, or 7.1 configuration.
According to prior art, a full decoding of all channels of the original multichannel audio content followed by downmixing to the channel configuration of the legacy playback system would be required. Apparently, such an approach is computationally inefficient since all channels of the original multichannel audio content needs to be decoded. There is thus a need for a coding scheme that allows to directly decode a downmix suitable for a legacy playback system
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